.\" Copyright (c) 1995 Martin Schulze <joey@infodrom.north.de>
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\" 1995-10-18  Martin Schulze  <joey@infodrom.north.de>
.\"	* first released
.\" 2002-09-22  Seth W. Klein  <sk@sethwklein.net>
.\"     * protocol numbers are now assigned by the IANA
.\"
.TH protocols 5 2024-05-02 "Linux man-pages 6.9.1"
.SH NAME
protocols \- protocols definition file
.SH DESCRIPTION
This file is a plain ASCII file, describing the various DARPA internet
protocols that are available from the TCP/IP subsystem.
It should be
consulted instead of using the numbers in the ARPA include files, or,
even worse, just guessing them.
These numbers will occur in the
protocol field of any IP header.
.P
Keep this file untouched since changes would result in incorrect IP
packages.
Protocol numbers and names are specified by the IANA
(Internet Assigned Numbers Authority).
.\" .. by the DDN Network Information Center.
.P
Each line is of the following format:
.P
.RS
.I protocol number aliases .\|.\|.
.RE
.P
where the fields are delimited by spaces or tabs.
Empty lines are ignored.
If a line contains a hash mark (#), the hash mark and the part
of the line following it are ignored.
.P
The field descriptions are:
.TP
.I protocol
the native name for the protocol.
For example
.IR ip ,
.IR tcp ,
or
.IR udp .
.TP
.I number
the official number for this protocol as it will appear within the IP
header.
.TP
.I aliases
optional aliases for the protocol.
.P
This file might be distributed over a network using a network-wide
naming service like Yellow Pages/NIS or BIND/Hesiod.
.SH FILES
.TP
.I /etc/protocols
The protocols definition file.
.SH SEE ALSO
.BR getprotoent (3)
.P
.UR http://www.iana.org\:/assignments\:/protocol\-numbers
.UE
